Intents and Locks with Intent

ABSTRACT

A computing device requests access to an application object from a remote storage system in order to locally execute application functionality without hosting application resources. An accessed object is associated with an intent in the storage system and locked. Locking an object in combination with an intent prevents computing devices that are not performing the intent from accessing the object. An intent defines one or more operations to be performed with the requested object, which are serialized as intent steps and stored in the storage system. Upon executing an intent step, the computing device stores a log entry at the storage system signifying the step&#39;s completion. A locked object remains locked until the log entries indicate every intent step as complete. Different computing devices can unlock a locked object by executing any incomplete steps of an intent associated with the locked object.

RELATED APPLICATIONS

This application claims priority under 35 USC 119 or 365 to China PatentApplication No. 201610864594.X, filed Sep. 29, 2016 and titled “Intentsand Locks with Intent”, the disclosure of which is incorporated byreference herein in its entirety.

BACKGROUND

As computing technology has advanced, distributed storage systems havebecome popular choices for deploying applications. Distributed storagesystems, such as cloud storage systems, offer reliable storage serviceswith simple application programming interfaces (APIs) that hide thedistributed nature of the underlying storage. This hidden distributednature alleviates the need for application developers to handledistributed-system issues such as data partitioning, fault tolerance,and load balancing. In distributed computing environments, applicationdata can be stored at a storage system while application computationsare performed by one or more computing devices located remotely from thestorage system.

Although storage system providers typically implement fault-toleranceprotocols, these storage systems are not without their problems. Forexample, different computing devices, computing device programs, andcomputing device virtual machines often request access to a singlestorage system object at the same time. While accessing an object,computing devices performing application computations can fail,application processes on devices can crash, and a network connecting thecomputing devices to the storage system can drop or reordercommunications. In order to address these and other problems, storagesystems can lock stored objects during access by a computing device.However, locks are not without their problems. One such problem is thata computing device accessing a locked object may fail to completeexecuting functionality associated with the locked object, causing thestorage system to lock an object indefinitely. Furthermore, storageservices tend to offer limited, low-level APIs that restrict applicationoperations to objects within a storage area. Thus, it remains difficultto develop applications for distributed computing environments.

SUMMARY

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter.

In accordance with one or more aspects, a computing device communicatesa request to a storage system for access to an object. The computingdevice provides the storage system with an intent associated with theobject. In response to providing the intent associated with the object,the computing device causes the storage system to lock the requestedobject and obtains access to the requested object. Using the obtainedobject, the computing device then executes one or more steps of theintent. Results of the executed one or more steps are communicated tothe storage system. Upon completing all steps of the intent, thecomputing device causes the storage system to unlock the locked object.

In accordance with one or more aspects, a computing device ascertainsthat an object is locked in a storage system. The computing deviceascertains an intent associated with the locked object. The computingdevice ascertains if the object has been locked for a threshold amountof time. If the object has not been locked for the threshold amount oftime, the computing device waits until the threshold amount of timeelapses. In response to determining that the object has been locked forthe threshold amount of time, the computing device ascertains one ormore incomplete steps of an intent associated with the locked object andexecutes the one or more incomplete steps. The computing devicecommunicates the results of the executed steps to the storage system.After executing all incomplete steps and communicating results of theexecuted steps of the intent associated with the locked object to thestorage system, the computing device causes the storage system to unlockthe locked object.

In accordance with one or more aspects, a storage system receives arequest from a computing device to access an object. The storage systemreceives an intent associated with the requested object from thecomputing device. In response to receiving the intent associated withthe requested object, the storage system locks the requested object andprovides the computing device with access to the requested object. Thestorage system receives an indication that the intent associated withthe requested object is complete. In response to ascertaining that theintent associated with the requested object is complete, the storagesystem unlocks the locked object.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description is described with reference to the accompanyingfigures. In the figures, the left-most digit(s) of a reference numberidentifies the figure in which the reference number first appears. Theuse of the same reference numbers in different instances in thedescription and the figures may indicate similar or identical items.Entities represented in the figures may be indicative of one or moreentities and thus reference may be made interchangeably to single orplural forms of the entities in the discussion.

FIG. 1 illustrates an example system implementing locks with intent forperforming application computations in accordance with one or moreembodiments.

FIG. 2 illustrates an example locks with intent system in accordancewith one or more embodiments.

FIG. 3 is a flowchart illustrating an example process for obtaining alock on a storage system object with an associated intent in accordancewith one or more embodiments.

FIG. 4 is a flowchart illustrating an example process for unlocking alocked storage system object with an associated intent in accordancewith one or more embodiments.

FIG. 5 is a flowchart illustrating an example process for locking arequested storage system object until an intent associated with theobject is complete in accordance with one or more embodiments.

FIG. 6 illustrates an example system that includes an example computingdevice that is representative of one or more systems and/or devices thatmay implement the various techniques described herein.

DETAILED DESCRIPTION

Storage system abstraction techniques for executing applicationfunctionality in a distributed computing environment are discussedherein. A plurality of computing devices are connected to the storagesystem via a network and are configured to execute operations for theapplication stored at the storage system. In one or more embodiments,individual ones of the plurality of computing devices are configured toexecute the operations using a plurality of program instances or virtualmachines running on the computing device. When a computing deviceexecutes application operations, the computing device requests access toone or more application objects stored at the storage system. Asdiscussed herein, an application object, or simply object, refers to alocation in storage system memory. An object can include data, avariable, executable code that can be used to perform a function ormethod of the application, or combinations thereof. In many situations,a computing device alters application data in an accessed storage systemobject when executing application operations. For example, a computingdevice may cause the storage system to create additional objects, deleteexisting objects, or update an object's value. An applicationcomputation module is implemented on each computing device, whichexecutes application functionality using application objects accessedfrom the storage system.

A locks with intent (LWI) system is implemented by each computing deviceconnected to the storage system. The LWI system provides an abstractrepresentation of a storage system's APIs and underlying storagecapabilities and organization. A computing device interacts with astorage system by assuming that the storage system provides an interfaceas represented by the LWI system. In order to enable communication witha range of different storage systems, the LWI system exposes a set ofAPIs to applications on the computing device that are supported amongthe range of different storage systems. These APIs enable a computingdevice to request objects from a storage system and communicate resultsof operations associated with objects back to the storage system. Whenthe computing device requests access to a storage system object in orderto execute application functionality, the computing device uses the LWIsystem to communicate an intent associated with the requested object tothe storage system.

An intent, as discussed herein, is an arbitrary snippet of code that isconfigured to contain both storage system operations and computingdevice operations associated with an object. For example, an intent canbe an object of a class with a “run” method and serialization routines.Thus, an intent indicates one or more actions or operations that are tobe performed with the requested object to execute applicationfunctionality. Each action or operation associated with an intent canalso be referred to as a “step”, and a single intent may require thecompletion of multiple steps. Using the LWI system, a computing devicerequests access to a storage system object and causes the storage systemto store an intent identifier associated with the requested object. Thisintent identifier indicates the intent associated with the requestedobject to both the storage system and other computing devices that mightrequest access to the requested object. Using the LWI system, thecomputing device can also cause the storage system to associate a lockwith the intent, which locks the requested object until one or moresteps of the intent are complete. This ensures a different computingdevice does not access a locked object while the computing device thatoriginally requested the object is performing steps associated with theintent.

Traditionally, a lock restricts access to a single computing deviceholding the lock, thereby ensuring that a different computing device isunable to access the locked object until the single computing devicecompletes executing application functionality associated with the lockedobject.

In order to address problems associated with traditional locks, acomputing device uses the LWI system to create and update an intenttable at the storage system that lists intents associated with objects.Specifically, when a computing device requests access to an object andindicates an intent associated with the requested object, the intent isadded to an intent table in the storage system. Each intent in theintent table is associated with an intent identifier, which correspondsto the intent identifier associated with the requested object, asdiscussed above. The intent table thus lists all intents associated withobjects in the storage system. In this manner, the LWI system enables acomputing device to ascertain an intent associated with an object, evenwhen the object is locked.

The LWI system additionally logs each computing device's execution ofintent steps in an execution log on the storage system through the useof distributed atomic affinity logging (DAAL). For each step in anintent, the LWI system enters a unique log entry in an execution tablein the storage system. Each log entry in the execution table signifiescompletion of an associated intent step, enabling the storage system torecord that one or more execution steps have been performed. Thisexecution table thus enables a plurality of computing devices toascertain what steps associated with an intent have been completed andwhat steps associated with an intent have yet to be completed. Forexample, in scenarios where multiple different computing devices areconcurrently executing the same intent with a single object, each of themultiple different computing devices can query the execution log toascertain whether a DAAL entry exists for an execution step. If a DAALentry exists for a specific step, each of the multiple differentcomputing devices skips performing execution of the specific step anduses a result of the specific step as indicated by the DAAL entry. Inthe absence of a DAAL entry for a given step, a computing deviceproceeds with executing the given step. When a computing device beginsexecution of a given step, it causes the storage system to generate aDAAL entry indicating that execution of the step has commenced. Uponcompleting execution of the given step, the computing devicecommunicates any results associated with execution of the given step tothe storage system and causes the storage system to update the DAALentry, signifying completion of this step. Any other computing devicerunning the same intent is thus able to ascertain that the given stephas already been executed and ascertain any results associated withexecution of the given step. This ensures execution of each intent stepexactly once, even in situations where multiple computing devices areconcurrently executing a common intent on an object.

The LWI system can also include an intent collector, which is configuredto interface with the storage system and poll the intent table andexecution log to identify incomplete intents associated with objects onthe storage system. The intent collector compares entries in theexecution log with intents in the intent table and identifies intentsteps that have not been completed within a threshold period of time. Inone or more embodiments, this threshold period of time is configurableby an administrator of the storage system. In one or moreimplementations, the intent collector identifies incomplete intentsbased on the absence of DAAL entries in the execution log. Alternativelyor additionally, the intent collector identifies incomplete intentsbased on DAAL entries indicating that an intent step has begun, but notyet completed, in the execution log. When the intent collectorascertains that an intent step has not been completed within thethreshold period of time, the intent collector executes the incompleteintent steps and enters DAAL entries in the execution log signifyingcompletion of the incomplete intent steps. In this manner, a computingdevice can use the intent collector to unlock a requested storage systemobject that was previously locked by a different computing device.

FIG. 1 is a block diagram illustrating an example system 100implementing storage system abstraction techniques for performingapplication computations in accordance with one or more embodiments.System 100 includes multiple (m) computing devices 102 that can eachcommunicate with a storage system 104 via a network 106. Network 106 canbe a variety of different networks, including the Internet, a local areanetwork (LAN), a public telephone network, an intranet, other publicand/or proprietary networks, combinations thereof, and so forth.

Each computing device 102 can be any one of a variety of different typesof computing devices, such as a desktop computer, a server computer, avirtual machine, a laptop or netbook computer, a mobile device (e.g., atablet or phablet device, a cellular or other wireless phone (e.g., asmartphone), a notepad computer, a mobile station), a wearable device(e.g., eyeglasses or head-mounted display (e.g., augmented reality (AR)or virtual reality (VR) eyeglasses or head-mounted display, watch,bracelet), an entertainment device (e.g., an entertainment appliance, aset-top box communicatively coupled to a display device, a gameconsole), one of a plurality of virtual machines running on a singlecomputing device, Internet of Things (IoT) devices (e.g., objects orthings with software, firmware, and/or hardware to allow communicationwith other devices), a television or other display device, an automotivecomputer, and so forth. Thus, each computing device 102 can range from afull resource device with substantial memory and processor resources(e.g., personal computers, game consoles) to a low-resource device withlimited memory and/or processing resources (e.g., traditional set-topboxes, hand-held game consoles). Different ones of computing devices 102can be the same or different types of computing devices. Thefunctionality discussed herein as performed by a computing device 102can additionally or alternatively be performed by one or more programsrunning on a hardware device.

Each computing device 102 includes one or more application computationmodules 108 that are configured to execute functionality of one or moreapplications stored at storage system 104. Generally, functionality ofone or more applications is executable through computer systemexecutable instructions, including routines, programs, objects,components, logic, data structures, and so on that perform particulartasks for an application. Application computation module 108 isapplication-independent and is thus configured to execute functionalityof various different types of applications. Through this configuration,computing devices 102 can implement a wide range of applications withoutlocally maintaining application resources.

Each computing device 102 additionally includes a locks with intent(LWI) system 110. LWI system 110 provides computing device 102 with acommon storage model that is an abstract representation of the storagesystem 104. By abstracting the storage system 104 with which computingdevice 102 is communicating, LWI system 110 enables the computing deviceto interface with various APIs of different storage systems. The variouscomponents and functionality of LWI system 110 are discussed in furtherdetail below with respect to FIG. 2.

Storage system 104 is implemented by one or more devices that can eachbe a variety of different types of computing devices. Similar to thediscussion of computing devices 102, the storage system 104 can beimplemented by devices ranging from full resources devices withsubstantial memory and processor resources to low-resource devices withlimited memory and/or processing resources. In one or more embodiments,storage system 104 is a cloud storage system, such as a Microsoft® AzureStorage system, an Amazon® DynamoDB system, a Google® Cloud Storagesystem, and so on. Alternatively, storage system 104 may be alarge-scale distributed storage system, such as an Apache® Cassandra™database, a MongoDB®, and so on.

Storage system 104 includes one or more objects 112, one or moreexecution logs 114, and one or more intent tables 116. Each object 112refers to a location in storage system memory, and thus may refer to oneof the plurality of rows of the one or more schemaless tables in theremote storage system. Additionally, as discussed herein the term“object” can interchangeably refer to a document, a partition or a tablein the remote storage system. Because objects 112 are stored in astorage system that is remote from a computing device accessing thestorage system, reference to an object 112 discussed herein correspondsto the object as stored in the remote storage system. Each object 112can be associated with a lock 118 and an intent identifier (ID) 120.

LWI system 110 enables a computing device to lock an object 112 whilethe computing device is accessing the object by associating the object112 with a lock 118 and an intent ID 120. The lock 118 and intent ID 120represent metadata associated with an object in the storage system. Thismetadata can be associated with an object and can be updated by a lockmanagement module of the LWI system 110, which is discussed in furtherdetail with respect to FIG. 2. For example, lock management module 204can associate lock 118 and intent ID 120 with object 112 through the useof invisible entries. An invisible entry, as discussed herein, is anentry in a storage system, such as storage system 104, which is strippedfrom (excluded from) any results returned to an application stored onthe storage system. In this manner, the entries are ascertainable bycomputing device 102 interfacing with the storage system 104, but remaininvisible to the application stored on the storage system.

A lock 118 is represented in metadata associated with an object 112 asan invisible Boolean attribute of the object. For example, a lock 118having value of 1 may indicate that the object 112 is locked, while avalue of 0 may indicate that the object is unlocked, or vice versa. Inorder to determine whether an object 112 is locked, a computing deviceimplementing LWI system 110 uses a Read API to interface with thestorage system storing object 112 and return a handle associated withthe object. A value of the lock 118 is returned in this handle to thecomputing device, informing the computing device whether the object 112is locked.

If a computing device ascertains that an object 112 is unlocked, thecomputing device can acquire a lock 118 on the object 112 by issuing aconditional update to the storage system. The computing device issuesthis conditional update including the returned handle from the Read APIoperation on the object 112 using APIs that are provided by LWI system110 and discussed in further detail with respect to FIG. 2. Thecomputing device obtains the lock 118 if, and only if, the conditionalupdate succeeds. To release the lock, the computing device issuesanother conditional update to reset the Boolean value of lock 118. Inaccordance with one or more embodiments, this conditional update dependson whether execution of an intent associated with the object iscomplete. Associating an intent with an object is discussed in furtherdetail below.

While an object 112 is locked, the lock prevents certain computingdevices from accessing the object. For example, when an object 112 islocked in the traditional sense, the traditional lock prevents anycomputing device that did not set the lock from reading, updating, ordeleting the locked object 112. As such, if a computing device holding alock 118 on an object 112 fails to release the lock, the object mayremain locked indefinitely. To address this problem, LWI system 110enables a computing device to associate an object and any correspondinglock with an intent ID 120.

As discussed herein, an intent is an arbitrary snippet of code that isconfigured to contain both storage system operations and computingdevice operations associated with an object. Thus, an intent specifiesone or more actions or operations that are to be performed with anobject. As discussed herein, individual actions or operations associatedwith an intent are referred to as “intent steps” or simply “steps”. Foran intent that includes a series of steps to be performed, these stepsare serialized and defined as part of the intent.

LWI system 110 associates every intent with a unique intent ID 120. LWIsystem 110 enables a computing device to associate an intent ID 120 withan object 112 in a storage system through the use of an invisible entry.As discussed above, this enables the computing device to enter an intentID 120 into metadata associated with an object 112 in the storagesystem. When a computing device implementing LWI system 110 associatesan intent ID 120 with an object 112, the LWI system 110 additionallyuploads the intent ID 120 and one or more steps associated with theintent ID to an intent table 116 stored in the storage system. Inaccordance with one or more embodiments, associating an intent ID 120with an object 112 and entering the intent ID 120 into the intent table116 is performed by a lock management module of the LWI system 110, asdiscussed in further detail with respect to FIG. 2. The intent table 116lists one or more intents based on their intent ID 120 and includes alist of the serialized intent steps. In accordance with one or moreembodiments, LWI system 110 creates a different intent table 116 in thestorage system for each different application hosted by the storagesystem.

A storage system's intent table 116 can be read by one or more computingdevices accessing the storage system. As discussed above, the one ormore computing devices can read an object 112 to identify an intent ID120 associated with the object. Accordingly, using the intent ID readfrom object 112, a computing device interfacing with the storage systemis able to query the intent table 116 to ascertain one or more stepsassociated with the intent ID. However, while the intent table 116 listsone or more steps associated with an intent, the intent table 116 alonedoes not provide an indication of whether execution of the one or moresteps has been completed.

In order to ensure that execution of an intent step is performed exactlyonce, a computing device implementing LWI system 110 is configured tocreate an execution log 114 in storage system 104. Execution log 114includes a list of one or more entries, associated with an intent ID120, signifying that execution of one or more intent steps has begun oris complete. A computing device implementing LWI system 110 updatesexecution log 114 when executing an intent step through the use ofdistributed atomic affinity logging (“DAAL”). DAAL collocates the resultof executing an intent step with the object 112 that the intent stepchanges. Thus, entries in a storage system's execution log 114 areassociated with an intent ID 120 and serialized to provide an indicationof execution progress, if any, of an intent. Specifically, while acomputing device executes an intent step, the LWI system 110 adds a newrow to the execution log 114 that lists an intent ID 120 and a stepnumber within the intent. For non-deterministic operations performed onthe computing device, such as the result of a random number generator,LWI system 110 stores any non-deterministic choices in the storagesystem's execution log 114. Similarly, for storage system operationsthat return results, such as read operations, the LWI system 110 causesthese results to be stored in the storage system execution log 114.

Entries in the execution log 114 prevent redundant execution of intentsteps to ensure exactly-once semantics. A computing device implementingLWI system 110 queries a storage system's execution log 114 beforeperforming an intent step and executes the intent step only in theabsence of an execution log entry corresponding to that step. Forexample, if an intent includes five sequential steps and the executionlog 114 indicates that steps one, two, and three are complete, thecomputing device uses any values for the completed steps that are storedin the execution log 114 and continues to execute steps four and five.

Intent step entries in the execution log 114 are collocated with anobject 112 being modified by the intent steps. Specifically, a computingdevice implementing the LWI system 110 creates the execution log 114within the same scope as an object 112 being modified. This enables acomputing device implementing LWI system 110 to atomically perform boththe intended update operation with the insertion of an entry into astorage system's execution log 114, using an AtomicBatchUpdate APIprovided by the LWI system 110, as discussed in further detail withrespect to FIG. 2. For locked objects associated with an unfinishedintent, when the execution log 114 includes entries for each step of anintent, a computing device implementing the LWI system 110 sends aconditional update to storage system 104 with the corresponding intentID 120 and causes the storage system 104 to release a lock 118 on theobject associated with the intent ID. Alternatively, in one or moreimplementations the final step in an intent is to unlock the lockedobject. Releasing a lock on an object can be performed by adjusting alock attribute in the object's metadata, as discussed above. Becausemultiple different computing devices can concurrently execute same ordifferent intents, this enables a computing device to ensure that anobject is not updated or deleted by a different computing device while adeclared intent is being performed with the object.

By associating a locked object 112 with an intent ID 120 and populatingthe storage system with information describing one or more stepsassociated with the intent in intent table 116, LWI system 110 causesthe storage system to include the requisite information for completingan intent associated with a locked object. Additionally, by populatingthe storage system with information indicating which of the one or moresteps are complete in execution log 114, LWI system 110 causes thestorage system to store information describing execution progressassociated with pending or incomplete intents. This enables a computingdevice to complete execution of an unfinished intent to unlock an objectin the event that the original computing device that locked the objectfails to complete the intent.

However, a computing device 102 interfacing with storage system 104using LWI system 110 can fail while holding a lock. For example,application processes running on the computing device can crash, anetwork connecting the computing device to the storage system can dropor reorder messages, or the entire computing device can ceasefunctioning. To account for these possible failures, LWI system 110enables any computing device to access a locked object, even if thecomputing device is different than a computing device that originallylocked the object, so long as the computing device requests access tothe object using the indent ID 120 associated with the locked object. Inthis manner, different application instances can finish executing anunfinished intent in the event of failure, while ensuring exactly-onceoperations for each step in an intent. However, an object 112 may remainlocked indefinitely if no computing devices request access to the lockedobject using the intent ID 120 associated with the locked object. Thissituation is resolved by implementing an intent collector module of theLWI system 110.

FIG. 2 illustrates an example LWI system 110 in accordance with one ormore embodiments. As discussed above, the LWI system 110 provides acomputing device with an abstracted model for interfacing with a remotestorage system, such as storage system 104 illustrated in FIG. 1. Inthis manner, a computing device interfacing with a remote storage systemusing LWI system 110 can access objects stored at the remote storagesystem without prior knowledge of the storage system's APIs or datastorage capabilities. For example, as illustrated in FIG. 1, LWI system110 enables computing device 102 to access objects 112 for one or moreapplications stored at storage system 104 without prior knowledge ofstorage system 104. In order to account for different data types, LWIsystem 110 models a storage system as including one or more schemalesstables that each include a plurality of partitions, which in turn eachinclude a plurality of rows. LWI system 110 thus models a remote storagesystem as including one or more objects 112, an execution log 114, andan intent table 116, as illustrated in FIG. 1.

LWI system 110 includes APIs 202 for executing various operations on aremote storage system. In one or more embodiments, APIs 202 includeoperations to Create, Read, Update, and Delete (CRUD) objects in astorage system. The Create API creates an object with a specified valuein a table of the storage system. The Read API returns a value of aspecified object in a table of the storage system. The Update APIupdates the value of a specified object in the storage system.Similarly, the Delete API deletes a specified object from the storagesystem. When a computing device interfacing with a storage system usesany of the Create, Read, and Update APIs, a handle representative of thecorresponding operation is returned to the computing device indicatingcompletion of the operation specified by the API.

APIs 202 additionally enable operations to Scan, UpdateIfUnchanged, andAtomicBatchUpdate storage system objects, such as objects 112 asillustrated in FIG. 1. The Scan API takes a storage system table and apredicate as parameters and returns a stream including all objects inthat table satisfying that predicate. For example, in one or moreembodiments the Scan predicate is “has a count attribute with valuegreater than 5”. The Scan API with this predicate would then return astream including every object in the identified table having anattribute value greater than five. However, an object that onlysatisfies the predicate during a portion of the scan will notnecessarily be included in the return stream. For example, if the objectwas created, updated, or deleted during the scan, the object may onlysatisfy the predicate during portions of the scan.

The UpdateIfUnchanged API considers whether an object has been updatedor deleted since a specified previous operation on that object. If theobject has been updated or deleted since a previous operation, which isidentifiable by a handle passed to the UpdateIfUnchanged API, theUpdateIfChanged operation does nothing. A computing device interfacingwith a remote storage system using the LWI system 110 can obtain handlesregarding object changes because each of the Create, Read, and UpdateAPI's operations return a handle representing that operation.

The AtomicBatchUpdate API enables the LWI system 110 to perform multipleupdate and insert operations atomically. As discussed herein, atomicoperations appear to occur concurrently and instantaneously to the hoststorage system. For example, atomic operations guarantee either that alloperations occur or that no operations occur, despite potential systemfailures. In order to ensure atomicity, the AtomicBatchUpdate API'soperations are limited to objects in the same scope. A scope, asdiscussed herein, refers to a system-specific parameter. For example, ascope may be a document, a table, a table partition, a table row, or anyother logical data collection supported by a storage system.

The APIs 202 enable a computing device implementing LWI system 110 tointerface with a variety of different distributed storage systems, evenif the different distributed storage systems offer different APIs. LWIsystem 110 ensures compatibility of APIs 202 with a remote storagesystem through the use of a shim. The shim is a layer that implementscalls of APIs 202 using APIs that are naturally supported by a storagesystem.

Using APIs 202, a computing device implementing LWI system 110 is ableto interact with one or more storage system objects, such as objects 112in storage system 104, as illustrated in FIG. 1, in order to executefunctionality for an application stored at the storage system.

LWI system 110 additionally includes lock management module 204. Lockmanagement module 204 implements locking and unlocking of applicationobjects stored in a storage system, such as storage system 104illustrated in FIG. 1. As discussed above and in further detail belowwith respect to FIGS. 3-5, lock management module 204 implements lockingand unlocking of application objects by associating storage systemobjects with locks and intent identifiers to ensure exactly-oncesemantics for all intents associated with the storage system objects.

To ensure that locked objects do not remain locked indefinitely, LWIsystem 110 additional includes intent collector module 206. Intentcollector module 206 is configured to ensure liveness in storage system104 by completing unfinished intent steps associated with locked objectsin the storage system.

A computing device implementing LWI system 110 employs the intentcollector module 206 to periodically query a storage system forunfinished intents and to complete any unfinished intent steps.Specifically, a computing device uses intent collector module 206 toperiodically poll the intent table of a storage system and compare thelisted intent steps against entries in the execution log to ascertainincomplete intent steps. The intent collector module 206 is configuredto poll the storage system at any suitable interval, such as once persecond, once per minute, and so on. If the intent collector module 206determines that a storage system object, such as one of objects 112 inFIG. 1, is locked for greater than a threshold amount of time, theintent collector module is configured to ascertain an intent IDassociated with the locked object as well as the incomplete stepsassociated with the intent ID. In accordance with one or moreembodiments, the intent collector module 206 ascertains that the objecthas been locked for a threshold amount of time by using the ascertainedintent ID to identify a corresponding intent in the intent table on thestorage system hosting the locked object. The intent collector module206 identifies a start time associated with the intent in the intenttable and compares the start time against a current time to determine anamount of time that the object has been locked. The threshold amount oftime may be configurable by a user of the computing device and may beany amount of time. In accordance with one or more embodiments, thethreshold amount of time is one second or less.

Accordingly, a computing device implementing the intent collector module206 of LWI system 110 can interface with a storage system to release anobject lock, even if the computing device was not responsible forsetting the lock, to obtain access to a locked object while ensuringexactly-once semantics of any associated intents. The intent collectormodule 206 thus ensures liveness in a storage system by completingunfinished intents despite failure of a computing device connected tothe storage system.

In one or more embodiments, the intent collector module 206 is alsoconfigured to perform garbage collection for a storage system'sexecution logs and intent tables, such as execution logs 114 and intenttables 116 of storage system 104, as illustrated in FIG. 1. Garbagecollecting execution logs 114 and intent tables 116 refers to thedeletion of entries in the execution logs 114 and deletion of intentsteps from intent tables 116. To prevent premature garbage collection,intent collector module 206 performs garbage collection in epochintervals. As discussed herein, an epoch refers to a configurableduration of time. In accordance with one or more embodiments, an epochmay be intent-specific and defined by a developer of an applicationassociated with the intent. For example, intent A may be associated with1 day epochs while intent B may be associated with 1 hour epochs. Forperforming garbage collecting, the intent collector module identifies anepoch n associated with an intent ID 120 using an intent's associatedstart time and does not perform garbage collection on entries in anexecution log 114 or intent table 116 that are associated with theintent ID until the intent ID is outdated. In accordance with one ormore embodiments, the intent collector module 206 identifies an intentID 120 as outdated during epoch n+2 and beyond.

In addition to ensuring exactly-once semantics for executing applicationfunctionality of applications in a distributed storage system, thetechniques discussed herein provide added storage system functionalitythat is not natively offered by the underling storage system.

For example, the techniques discussed herein enable reliablesnapshotting of storage systems. By associating storage system objectswith locks and intents, the techniques herein eliminate interleavingsduring snapshotting operations that might be left by a second computingdevice accessing the object during snapshotting by a first computingdevice. Similarly, the techniques discussed herein enable livere-partitioning of storage system tables that enables concurrentoperations. Re-partitioning refers to the process of migrating a storagesystem object from one location in the storage system to anotherlocation. By implementing locks with intents on objects, the techniquesdiscussed herein prevent different computing devices from updating orreading objects during re-partitioning. Live re-partitioning using thelocks with intent techniques discussed herein enables a storage systemto account for partitions that exceed a system-imposed partition sizelimit without negatively affecting system liveness. The techniquesdiscussed herein additionally enable use of secondary indices. Asecondary index for a storage system table T is a separate table T′configured to allow quick lookups into T. Because storage systems do notnatively support multi-table atomic transactions, conventional use ofsecondary indices results in situations where the content of T and T′ isinconsistent with each other. However, the techniques discussed hereinenable concurrent updating, inserting, and deleting rows in T and T′ bydefining the various operations as steps of a single intent. Because thetechniques discussed herein require “all or nothing” performance ofintent steps, secondary index problems caused by intermediate failuresare eliminated. Further, the techniques discussed herein enabletransactions among different storage system tables and partitions byusing intents as transaction coordinators.

FIG. 3 is a flowchart illustrating an example process 300 for obtaininga lock on a storage system object with an associated intent inaccordance with one or more embodiments. Process 300 is carried out by acomputing device implementing a locks with intent system and interfacingwith a storage system, such as a computing device 102 implementing LWIsystem 110 and interfacing with storage system 104, as illustrated inFIG. 1. Process 300 can be implemented in software, firmware, hardware,or combinations thereof. Process 300 is shown as a set of acts and isnot limited to the order shown for performing the operations of thevarious acts. Process 300 is an example process for obtaining a lock ona storage system object with an associated intent in accordance with oneor more embodiments; additional discussions of obtaining a lock on astorage system object with an associated intent are included herein withreference to different figures.

In process 300, a computing device communicates a request to a storagesystem for access to an object (act 302). The requested object cancomprise a table in the storage system, a partition of a table in thestorage system, or a row of a table in the storage system. The requestedobject includes application data for an application stored at thestorage system and is useable by the computing device to executeapplication functionality for the application stored at the storagesystem.

The computing device additionally provides the storage system with anintent associated with the object (act 304). The communicated intent isan arbitrary snippet of code that accompanies the request and indicatesone or more computing device operations to be performed with therequested object. Additionally or alternatively, the communicated intentindicates one or more storage system operations to be performed with therequested object. The communicated intent includes at least one step,which details computing device and/or storage system operations to beperformed with the requested object, as discussed above. The stepsassociated with the intent are listed in an intent table stored on thestorage system and are associated with an intent ID that identifies theintent. The intent ID is entered as metadata associated with the objectin the storage system, as discussed above.

In response to providing the storage system with the intent associatedwith the object, the computing device causes the storage system to lockthe requested object (act 306). Locking the requested object prohibitsother computing devices from accessing the object while it is locked. Inaccordance with one or more embodiments, a computing device causes thestorage system to lock the object by setting a Boolean value as metadataassociated with the object in the storage system, which indicates thatthe object is locked. The computing device is configured to set aBoolean value as metadata associated with the object via an invisibleentry in the storage system.

The computing device obtains access to the requested object in responseto obtaining the lock on the object (act 308). Obtaining access to therequested object comprises obtaining application data for theapplication stored at the storage system that is useable by thecomputing device to execute application functionality for theapplication, as discussed above.

After the computing device obtains access to the requested object, thecomputing device executes one or more steps of the intent associatedwith the object (act 310). In accordance with one or more embodiments,executing the one or more steps of the intent includes performing one ormore actions or operations associated with application functionalityusing an application computation module of the computing device.

After the computing device executes an intent step, the computing devicecommunicates one or more results of the executed step to the storagesystem (act 312). Results of an executed intent step are communicatedthrough distributed atomic affinity logging, which refers to the processof collocating the result of a step's execution in the storage systemnear the object that the step's execution changes. Specifically, thecomputing device communicates a log entry signifying the completion ofan intent step to the storage system and causes the storage system toupdate an execution table with the communicated log entries. Thesecommunicated log entries are invisible to applications stored on thestorage system, but are ascertainable by computing devices that executeapplication functionality on behalf of the applications. This enablesmultiple computing devices to ascertain an execution status of intentsteps for an intent associated with a locked object.

After the computing device executes each step of the intent andcommunicates results of the executed steps to the storage system, thecomputing device causes the storage system to unlock the locked object(act 314). Unlocking the locked object permits the storage system toprovide other computing devices with access to the unlocked object. Inaccordance with one or more embodiments, a computing device causes thestorage system to unlock the locked object by adjusting a Boolean valuepreviously set by the computing device to indicate whether the object islocked. As discussed above, this Boolean value is represented inmetadata associated with the object in the storage system. The computingdevice is configured to adjust the Boolean value by communicating aninvisible entry associated with the locked object to the storage system.

FIG. 4 is a flowchart illustrating an example process 400 for unlockinga locked storage system object with an associated intent in accordancewith one or more embodiments. Process 400 is carried out by a computingdevice implementing a locks with intent system and interfacing with astorage system, such as a computing device 102 implementing LWI system110 and interfacing with storage system 104, as illustrated in FIG. 1.Process 400 can be implemented in software, firmware, hardware, orcombinations thereof. Process 400 is shown as a set of acts and is notlimited to the order shown for performing the operations of the variousacts. Process 400 is an example process for unlocking a locked storagesystem object with an associated intent in accordance with one or moreembodiments; additional discussions of unlocking a locked storage systemobject with an associated intent are included herein with reference todifferent figures.

In process 400, a computing device ascertains that an object in astorage system is locked (act 402). In accordance with one or moreembodiments, the computing device ascertains that the object is lockedby inspecting metadata in the storage system that is associated with theobject and identifying a Boolean value indicating a lock in themetadata. In accordance with one or more embodiments, the computingdevice ascertains that the object is locked in response to requestingaccess to the locked object.

In response to ascertaining that the object is locked, the computingdevice ascertains an intent associated with the locked object (act 404).In accordance with one or more embodiments, the computing deviceascertains the intent associated with the locked object by inspectingmetadata in the storage system that is associated with the object andidentifying an intent ID that identifies an intent in the metadata. Inaccordance with one or more embodiments, the computing device ascertainsan intent associated with a locked object in response to requestingaccess to the locked object.

The computing device then ascertains if the object has been locked for athreshold amount of time (act 406). In accordance with one or moreembodiments, the computing device ascertains if the object has beenlocked for a threshold amount of time by using the ascertained intent IDto identify a corresponding intent listed in an intent table on thestorage system. The computing device identifies a start time associatedwith the intent that corresponds to the intent ID and compares itagainst a current time to determine an amount of time that the objecthas been locked. In accordance with one or more embodiments, thethreshold amount of time is specific to an intent associated with theobject and is indicated as metadata in the intent table. The thresholdamount of time may be specified by a user of the computing device or maybe pre-specified by an application developer.

If the computing device ascertains that the object has not been lockedfor the threshold amount of time, the computing device waits until thethreshold amount of time has elapsed (act 408). Waiting until thethreshold amount of time has elapsed allows another computing devicethat may be executing one or more steps associated with an intent tofinish executing these steps.

If the computing device ascertains that the object has been locked forthe threshold amount of time or longer, the computing device ascertainsincomplete steps of an intent associated with the locked object (act410). The computing device ascertains incomplete steps of an intent byusing the ascertained intent ID to identify a corresponding intent andone or more steps of the corresponding intent, which are listed in theintent table on the storage system. Upon identifying the one or moresteps of the corresponding intent, the computing device ascertains whichof the one or more intent steps lack corresponding entries in anexecution log stored in the storage system. As discussed above, an entryin the execution log indicates that execution of an intent step iscomplete, thus the absence of an entry corresponding to an intent steprepresents an incomplete intent step.

In response to ascertaining the incomplete steps of the intentassociated with the locked object, the computing device executes theincomplete steps (act 412). In accordance with one or more embodiments,execution of the incomplete steps is performed by an intent collectormodule of the computing device.

After executing the incomplete intent steps, the computing devicecommunicates results of the executed steps to the storage system (act414). Results of an executed intent step are communicated throughdistributed atomic affinity logging, which refers to the process ofcollocating the result of a step's execution in the storage system nearthe object that the step's execution changes. Specifically, thecomputing device communicates a log entry signifying the completion ofan intent step to the storage system and causes the storage system toupdate the execution table with the communicated log entries. Thesecommunicated log entries are invisible to applications stored on thestorage system, but are ascertainable by computing devices that executeapplication functionality on behalf of the applications. This enablesmultiple computing devices to ascertain an execution status of intentsteps for an intent associated with a locked object.

After the computing device executes each incomplete step andcommunicates results of the executed steps to the storage system, thecomputing device causes the storage system to unlock the locked object(act 416). Unlocking the locked object permits the storage system toprovide other computing devices with access to the unlocked object. Inaccordance with one or more embodiments, a computing device causes thestorage system to unlock the locked object by adjusting a Boolean valuepreviously set by the computing device to indicate whether the object islocked. As discussed above, this Boolean value is represented inmetadata associated with the object in the storage system. The computingdevice is configured to adjust the Boolean value by communicating aninvisible entry associated with the locked object to the storage system.

FIG. 5 is a flowchart illustrating an example process 500 for locking arequested storage system object until an intent associated with theobject is complete in accordance with one or more embodiments. Process500 is carried out by a computing device implementing a storage system,such as storage system 104 of FIG. 1, and can be implemented insoftware, firmware, hardware, or combinations thereof. Process 500 isshown as a set of acts and is not limited to the order shown forperforming the operations of the various acts. Process 500 is an exampleprocess for locking a requested storage system object until an intentassociated with the object is complete in accordance with one or moreembodiments; additional discussions of locking a requested storagesystem object until an intent associated with the object are includedherein with reference to different figures.

In process 500, a request to access an object is received from acomputing device (act 502). The requested object can comprise apartition in a storage system, a table in the storage system, or a rowof a table in the storage system. In accordance with one or moreembodiments, the requested object includes application data for anapplication stored at the storage system and that is useable by thecomputing device to execute application functionality for theapplication stored at the storage system.

An intent associated with the requested object is received from thecomputing device (act 504). The received intent is an arbitrary snippetof code that may accompany the request and indicates one or morecomputing device operations to be performed with the requested object.Additionally or alternatively, the communicated intent indicates one ormore storage system operations to be performed with the requestedobject. The communicated intent includes at least one step, whichdetails computing device and/or storage system operations to beperformed with the requested object, as discussed above. The at leastone step associated with the intent is entered in an intent table storedon the storage system and is associated with the intent as well as anintent ID that identifies the intent. The intent ID is entered asmetadata associated with the object in the storage system, as discussedabove.

In response to receiving the intent associated with the requestedobject, the computing device implementing the storage system locks therequested object (act 506). Locking the requested object prohibitscomputing devices from accessing the object while it is locked unlessthe computing devices execute intent steps associated with the lock. Inaccordance with one or more embodiments, a computing device causes thestorage system to lock the object by setting a Boolean value as metadataassociated with the object in the storage system, which indicates thatthe object is locked.

In response to locking the requested object, the computing deviceimplementing the storage system provides the requested object to thecomputing device that requested the object (act 508). In accordance withone or more embodiments, providing access to the requested objectcomprises providing application data for an application stored by thestorage system. This application data is useable by the requestingcomputing device to execute application functionality for theapplication, as discussed above.

The computing device implementing the storage system then receives anindication that the intent associated with the requested object iscomplete (act 510). In accordance with one or more embodiments,receiving an indication that the associated intent is complete comprisesreceiving results associated with executing one or more intent stepsthrough distributed atomic affinity logging. Upon receiving resultsassociated with executing one or more intent steps, the computing deviceimplementing the storage system collocates the results in the storagesystem using an execution table. This execution table is populated withlog entries, which signify the completion of an intent step, asdiscussed above. These communicated log entries are invisible toapplications stored on the storage system, but are ascertainable bycomputing devices that execute application functionality on behalf ofthe applications. This enables multiple computing devices to ascertainan execution status of intent steps for an intent associated with alocked object.

Upon receiving an indication that all steps of the intent associatedwith the requested object are complete, the computing deviceimplementing the storage system unlocks the requested object (act 512).Unlocking the locked object permits the storage system to provide othercomputing devices with access to the unlocked object. In accordance withone or more embodiments, the storage system unlocks the requested objectby adjusting a Boolean value associated with the requested object. Asdiscussed above, this Boolean value is represented in metadataassociated with the object in the storage system.

Although the techniques discussed herein have been made with referenceto a distributed computing environment where a computing device isimplemented remotely from a storage system, additionally oralternatively the techniques discussed herein can be implemented on asingle computing device. For example, returning to FIG. 1, a single oneof computing devices 102 can include multiple instances of theapplication computation module 108, each associated with its own LWIsystem 110. In a single computing device environment, the multipleinstances of the application computation module 108 can be connected toone another via a system bus or other data and command transfer system,which provides similar functionality to that of network 104. In a singlecomputing device 102 implementation, the multiple instances of theapplication computation module 108 access objects from memory/storagecapacity provided by one or more computer-readable media of thecomputing device 102. In this implementation, the memory/storage of thecomputing device represents functionality of the storage system 104, asdescribed herein. Thus, the techniques herein can be used both indistributed computing environments as well as a single computing deviceenvironment.

Although particular functionality is discussed herein with reference toparticular modules, it should be noted that the functionality ofindividual modules discussed herein can be separated into multiplemodules, and/or at least some functionality of multiple modules can becombined into a single module. Additionally, a particular modulediscussed herein as performing an action includes that particular moduleitself performing the action, or alternatively that particular moduleinvoking or otherwise accessing another component or module thatperforms the action (or performs the action in conjunction with thatparticular module). Thus, a particular module performing an actionincludes that particular module itself performing the action and/oranother module invoked or otherwise accessed by that particular moduleperforming the action.

FIG. 6 illustrates an example system generally at 600 that includes anexample computing device 602 that is representative of one or moresystems and/or devices that may implement the various techniquesdescribed herein. The computing device 602 may be, for example, a serverof a service provider, one of a plurality of virtual machinesimplemented on a full resource computing device, a device associatedwith a client (e.g., client device), an on-chip system, and/or any othersuitable computing device or computing system.

The example computing device 602 as illustrated includes a processingsystem 604, one or more computer-readable media 606, and one or more I/OInterfaces 608 that are communicatively coupled, one to another.Although not shown, the computing device 602 may further include asystem bus or other data and command transfer system that couples thevarious components, one to another. A system bus can include any one orcombination of different bus structures, such as a memory bus or memorycontroller, a peripheral bus, a universal serial bus, and/or a processoror local bus that utilizes any of a variety of bus architectures. Avariety of other examples are also contemplated, such as control anddata lines.

The processing system 604 is representative of functionality to performone or more operations using hardware. Accordingly, the processingsystem 604 is illustrated as including hardware elements 610 that may beconfigured as processors, functional blocks, and so forth. This mayinclude implementation in hardware as an application specific integratedcircuit or other logic device formed using one or more semiconductors.The hardware elements 610 are not limited by the materials from whichthey are formed or the processing mechanisms employed therein. Forexample, processors may be comprised of semiconductor(s) and/ortransistors (e.g., electronic integrated circuits (ICs)). In such acontext, processor-executable instructions may beelectronically-executable instructions.

The computer-readable media 606 is illustrated as includingmemory/storage 612. The memory/storage 612 represents memory/storagecapacity associated with one or more computer-readable media. Thememory/storage 612 may include volatile media (such as random accessmemory (RAM)) and/or nonvolatile media (such as read only memory (ROM),Resistive RAM (ReRAM), Flash memory, optical disks, magnetic disks, andso forth). The memory/storage 612 may include fixed media (e.g., RAM,ROM, a fixed hard drive, and so on) as well as removable media (e.g.,Flash memory, a removable hard drive, an optical disc, and so forth).The computer-readable media 606 may be configured in a variety of otherways as further described below.

The one or more input/output interface(s) 608 are representative offunctionality to allow a user to enter commands and information tocomputing device 602, and also allow information to be presented to theuser and/or other components or devices using various input/outputdevices. Examples of input devices include a keyboard, a cursor controldevice (e.g., a mouse), a microphone (e.g., for voice inputs), ascanner, touch functionality (e.g., capacitive or other sensors that areconfigured to detect physical touch), a camera (e.g., which may employvisible or non-visible wavelengths such as infrared frequencies todetect movement that does not involve touch as gestures), and so forth.Examples of output devices include a display device (e.g., a monitor orprojector), speakers, a printer, a network card, tactile-responsedevice, and so forth. Thus, the computing device 602 may be configuredin a variety of ways as further described below to support userinteraction.

The computing device 602 also includes a locks with intent (LWI) system614. The LWI system 614 provides various functionality to lock objectswith an associated intent and unlock objects by completing steps of anassociated intent as discussed above. The LWI system 614 can implement,for example, the LWI system 110 of FIG. 1 or FIG. 2.

Various techniques may be described herein in the general context ofsoftware, hardware elements, or program modules. Generally, such modulesinclude routines, programs, objects, elements, components, datastructures, and so forth that perform particular tasks or implementparticular abstract data types. The terms “module,” “functionality,” and“component” as used herein generally represent software, firmware,hardware, or a combination thereof. The features of the techniquesdescribed herein are platform-independent, meaning that the techniquesmay be implemented on a variety of computing platforms having a varietyof processors.

An implementation of the described modules and techniques may be storedon or transmitted across some form of computer-readable media. Thecomputer-readable media may include a variety of media that may beaccessed by the computing device 602. By way of example, and notlimitation, computer-readable media may include “computer-readablestorage media” and “computer-readable signal media.”

“Computer-readable storage media” refers to media and/or devices thatenable persistent storage of information and/or storage that istangible, in contrast to mere signal transmission, carrier waves, orsignals per se. Thus, computer-readable storage media refers tonon-signal bearing media. The computer-readable storage media includeshardware such as volatile and non-volatile, removable and non-removablemedia and/or storage devices implemented in a method or technologysuitable for storage of information such as computer readableinstructions, data structures, program modules, logic elements/circuits,or other data. Examples of computer-readable storage media may include,but are not limited to, RAM, ROM, EEPROM, flash memory or other memorytechnology, CD-ROM, digital versatile disks (DVD) or other opticalstorage, hard disks, magnetic cassettes, magnetic tape, magnetic diskstorage or other magnetic storage devices, or other storage device,tangible media, or article of manufacture suitable to store the desiredinformation and which may be accessed by a computer.

“Computer-readable signal media” refers to a signal-bearing medium thatis configured to transmit instructions to the hardware of the computingdevice 602, such as via a network. Signal media typically may embodycomputer readable instructions, data structures, program modules, orother data in a modulated data signal, such as carrier waves, datasignals, or other transport mechanism. Signal media also include anyinformation delivery media. The term “modulated data signal” means asignal that has one or more of its characteristics set or changed insuch a manner as to encode information in the signal. By way of example,and not limitation, communication media include wired media such as awired network or direct-wired connection, and wireless media such asacoustic, RF, infrared, and other wireless media.

As previously described, the hardware elements 610 and computer-readablemedia 606 are representative of instructions, modules, programmabledevice logic and/or fixed device logic implemented in a hardware formthat may be employed in some embodiments to implement at least someaspects of the techniques described herein. Hardware elements mayinclude components of an integrated circuit or on-chip system, anapplication-specific integrated circuit (ASIC), a field-programmablegate array (FPGA), a complex programmable logic device (CPLD), and otherimplementations in silicon or other hardware devices. In this context, ahardware element may operate as a processing device that performsprogram tasks defined by instructions, modules, and/or logic embodied bythe hardware element as well as a hardware device utilized to storeinstructions for execution, e.g., the computer-readable storage mediadescribed previously.

Combinations of the foregoing may also be employed to implement varioustechniques and modules described herein. Accordingly, software,hardware, or program modules and other program modules may beimplemented as one or more instructions and/or logic embodied on someform of computer-readable storage media and/or by one or more hardwareelements 610. The computing device 602 may be configured to implementparticular instructions and/or functions corresponding to the softwareand/or hardware modules. Accordingly, implementation of modules as amodule that is executable by the computing device 602 as software may beachieved at least partially in hardware, e.g., through use ofcomputer-readable storage media and/or hardware elements 610 of theprocessing system. The instructions and/or functions may beexecutable/operable by one or more articles of manufacture (for example,one or more computing devices 602 and/or processing systems 604) toimplement techniques, modules, and examples described herein.

As further illustrated in FIG. 6, the example system 600 enablesubiquitous environments for a seamless user experience when runningapplications on a personal computer (PC), a television device, and/or amobile device. Services and applications run substantially similar inall three environments for a common user experience when transitioningfrom one device to the next while utilizing an application, playing avideo game, watching a video, and so on.

In the example system 600, multiple devices are interconnected through acentral computing device. The central computing device may be local tothe multiple devices or may be located remotely from the multipledevices. In one or more embodiments, the central computing device may bea cloud of one or more server computers that are connected to themultiple devices through a network, the Internet, or other datacommunication link.

In one or more embodiments, this interconnection architecture enablesfunctionality to be delivered across multiple devices to provide acommon and seamless experience to a user of the multiple devices. Eachof the multiple devices may have different physical requirements andcapabilities, and the central computing device uses a platform to enablethe delivery of an experience to the device that is both tailored to thedevice and yet common to all devices. In one or more embodiments, aclass of target devices is created and experiences are tailored to thegeneric class of devices. A class of devices may be defined by physicalfeatures, types of usage, or other common characteristics of thedevices.

In various implementations, the computing device 602 may assume avariety of different configurations, such as for computer 616, mobile618, and television 620 uses. Each of these configurations includesdevices that may have generally different constructs and capabilities,and thus the computing device 602 may be configured according to one ormore of the different device classes. For instance, the computing device602 may be implemented as the computer 616 class of a device thatincludes a personal computer, desktop computer, a multi-screen computer,laptop computer, netbook, server, and so on.

The computing device 602 may also be implemented as the mobile 618 classof device that includes mobile devices, such as a mobile phone, portablemusic player, portable gaming device, a tablet computer, a multi-screencomputer, and so on. The computing device 602 may also be implemented asthe television 620 class of device that includes devices having orconnected to generally larger screens in casual viewing environments.These devices include televisions, set-top boxes, gaming consoles, andso on.

The techniques described herein may be supported by these variousconfigurations of the computing device 602 and are not limited to thespecific examples of the techniques described herein.

In the discussions herein, various different embodiments are described.It is to be appreciated and understood that each embodiment describedherein can be used on its own or in connection with one or more otherembodiments described herein. Further aspects of the techniquesdiscussed herein relate to one or more of the following embodiments.

A method implemented in a computing device, the method comprising:communicating, to a storage system, a request for access to an object;providing, to the storage system, an intent associated with the object;obtaining access to the object in response to providing the intentassociated with the object; executing one or more steps of the intentassociated with the object; and communicating, to the storage system,results of the one or more steps of the intent associated with theobject, enabling the storage system to record that the one or more stepshave been performed and ensuring execution of each step of the intentexactly once.

Alternatively or in addition to any of the above described methods, anyone or combination of: wherein the one or more steps of the intentassociated with the object describe one or more computing deviceoperations or storage system operations to be performed with at leastthe object; wherein the object comprises a location in memory of thestorage system, the location comprising at least a portion of one of atable in the storage system, a partition of a table in the storagesystem, or a row of a table in the storage system; wherein providing theintent associated with the object comprises providing an intentidentifier of the intent associated with the object to the storagesystem, causing the storage system to update metadata associated withthe object to include an intent identifier of the intent associated withthe object, and causing the storage system to include, in an intenttable, a serialized listing of the one or more steps of the intentassociated with the object; wherein communicating the results of the oneor more steps of the intent associated with the object comprises causingthe storage system to generate an execution log that includes one ormore entries, wherein individual ones of the one or more entriesindicate that the computing device has completed executing acorresponding individual one of the one or more steps of the intentassociated with the object; the method further comprising causing thestorage system to lock the object as part of an execution of a firststep of the intent; wherein causing the storage system to lock theobject prevents a computing device that is not requesting access to theobject in order to perform the one or more steps of the intentassociated with the object from accessing the object until execution ofthe intent associated with the object is complete; wherein causing thestorage system to lock the object allows one or more different computingdevices that are requesting access to the object in order to perform theone or more steps of the intent associated with the object to access theobject.

A method implemented in a computing device, the method comprising:ascertaining that an object stored in a storage system is locked;ascertaining an intent that is associated with the locked object;ascertaining one or more incomplete steps of the intent associated withthe locked object; executing the one or more incomplete steps of theintent; communicating results of the executed one or more steps of theintent to the storage system; and causing the storage system to unlockthe object in response to communicating the results of the executed oneor more steps of the intent to the storage system.

Alternatively or in addition to any of the above described methods, anyone or combination of: wherein ascertaining that the object stored inthe storage system is locked is performed in response to requestingaccess to the object; wherein ascertaining the intent associated withthe locked object comprises ascertaining an intent identifier of theintent, the intent identifier being included in metadata for the objectstored in the storage system; wherein ascertaining the one or moreincomplete steps of the intent associated with the object comprisesascertaining an intent identifier of the intent, ascertaining a list ofone or more steps associated with the intent using the intentidentifier, the list of one or more steps including the one or moreincomplete steps, polling an execution log of the storage system toascertain if any of the list of one or more steps are complete, andascertaining the one or more incomplete steps of the intent based on anabsence of one or more log entries in the execution log; wherein the oneor more incomplete steps of the intent associated with the objectdescribe one or more computing device operations or storage systemoperations to be performed with the object; wherein the computing deviceis different from a computing device that caused the storage system tolock the object; wherein the storage system is implemented remotely fromthe computing device in a distributed computing environment; the methodfurther comprising ascertaining whether the locked object has beenlocked for a threshold amount of time and waiting, by the computingdevice, for the threshold amount of time to elapse in response todetermining that the locked object has not been locked for the thresholdamount of time; wherein the threshold amount of time is dependent on theintent associated with the object; wherein ascertaining whether thelocked object has been locked for the threshold amount of time comprisesascertaining a start time associated with the intent, comparing thestart time with a current time to determine an elapsed time of theintent, and comparing the elapsed time against the threshold amount oftime, wherein the object is locked for the threshold amount of time ifthe elapsed time is of a duration that is longer than the thresholdamount of time.

A storage system comprising: a processor; and a computer-readablestorage medium having stored thereon multiple instructions thatimplement a platform of the computing device and that, responsive toexecution by the processor, cause the processor to: receive a requestfrom a computing device for access to an object; receive, from thecomputing device, an intent associated with the object; provide thecomputing device with access to the object in response to receiving theintent associated with the object; receive an indication that executionof one or more steps of the intent associated with the object iscomplete; and enter one or more entries into an execution log,individual ones of the one or more entries indicating completion of oneof the one or more steps of the intent and ensuring execution of each ofthe one or more steps of the intent exactly once.

Alternatively or in addition to any of the above described systems, anyone or combination of: the multiple instructions further causing theprocessor to lock the object and prevent a computing device that is notrequesting the object in order to perform the one or more steps of theintent associated with the object in response to receiving the intentassociated with the object.

Although the subject matter has been described in language specific tostructural features and/or methodological acts, it is to be understoodthat the subject matter defined in the appended claims is notnecessarily limited to the specific features or acts described above.Rather, the specific features and acts described above are disclosed asexample forms of implementing the claims.

What is claimed is:
 1. A method implemented in a computing device, themethod comprising: communicating, to a storage system, a request foraccess to an object; providing, to the storage system, an intentassociated with the object; obtaining access to the object in responseto providing the intent associated with the object; executing one ormore steps of the intent associated with the object; and communicating,to the storage system, results of the one or more steps of the intentassociated with the object, enabling the storage system to record thatthe one or more steps have been performed and ensuring execution of eachstep of the intent exactly once.
 2. The method of claim 1, wherein theone or more steps of the intent associated with the object describe oneor more computing device operations or storage system operations to beperformed with at least the object.
 3. The method of claim 1, whereinthe object comprises a location in memory of the storage system, thelocation comprising at least a portion of one of a table in the storagesystem, a partition of a table in the storage system, or a row of atable in the storage system.
 4. The method of claim 1, wherein providingthe intent associated with the object comprises: providing an intentidentifier of the intent associated with the object to the storagesystem; causing the storage system to update metadata associated withthe object to include an intent identifier of the intent associated withthe object; and causing the storage system to include, in an intenttable, a serialized listing of the one or more steps of the intentassociated with the object.
 5. The method of claim 1, whereincommunicating the results of the one or more steps of the intentassociated with the object comprises causing the storage system togenerate an execution log that includes one or more entries, whereinindividual ones of the one or more entries indicate that the computingdevice has completed executing a corresponding individual one of the oneor more steps of the intent associated with the object.
 6. The method ofclaim 1, further comprising causing the storage system to lock theobject as part of an execution of a first step of the intent.
 7. Themethod of claim 6, wherein causing the storage system to lock the objectprevents a computing device that is not requesting access to the objectin order to perform the one or more steps of the intent associated withthe object from accessing the object until execution of the intentassociated with the object is complete.
 8. The method of claim 6,wherein causing the storage system to lock the object allows one or moredifferent computing devices that are requesting access to the object inorder to perform the one or more steps of the intent associated with theobject to access the object.
 9. A method implemented in a computingdevice, the method comprising: ascertaining that an object stored in astorage system is locked; ascertaining an intent that is associated withthe locked object; ascertaining one or more incomplete steps of theintent associated with the locked object; executing the one or moreincomplete steps of the intent; communicating results of the executedone or more steps of the intent to the storage system; and causing thestorage system to unlock the object in response to communicating theresults of the executed one or more steps of the intent to the storagesystem.
 10. The method of claim 9, wherein ascertaining that the objectstored in the storage system is locked is performed in response torequesting access to the object.
 11. The method of claim 9, whereinascertaining the intent associated with the locked object comprisesascertaining an intent identifier of the intent, the intent identifierbeing included in metadata for the object stored in the storage system.12. The method of claim 9, wherein ascertaining the one or moreincomplete steps of the intent associated with the object comprises:ascertaining an intent identifier of the intent; ascertaining a list ofone or more steps associated with the intent using the intentidentifier, the list of one or more steps including the one or moreincomplete steps; polling an execution log of the storage system toascertain if any of the list of one or more steps are complete; andascertaining the one or more incomplete steps of the intent based on anabsence of one or more log entries in the execution log.
 13. The methodof claim 9, wherein the one or more incomplete steps of the intentassociated with the object describe one or more computing deviceoperations or storage system operations to be performed with the object.14. The method of claim 9, wherein the computing device is differentfrom a computing device that caused the storage system to lock theobject.
 15. The method of claim 9, wherein the storage system isimplemented remotely from the computing device in a distributedcomputing environment.
 16. The method of claim 9, further comprisingascertaining whether the locked object has been locked for a thresholdamount of time and waiting, by the computing device, for the thresholdamount of time to elapse in response to determining that the lockedobject has not been locked for the threshold amount of time.
 17. Themethod of claim 16, wherein the threshold amount of time is dependent onthe intent associated with the object.
 18. The method of claim 16,wherein ascertaining whether the locked object has been locked for thethreshold amount of time comprises: ascertaining a start time associatedwith the intent; comparing the start time with a current time todetermine an elapsed time of the intent; and comparing the elapsed timeagainst the threshold amount of time, wherein the object is locked forthe threshold amount of time if the elapsed time is of a duration thatis longer than the threshold amount of time.
 19. A storage systemcomprising: a processor; and a computer-readable storage medium havingstored thereon multiple instructions that implement a platform of thecomputing device and that, responsive to execution by the processor,cause the processor to: receive a request from a computing device foraccess to an object; receive, from the computing device, an intentassociated with the object; provide the computing device with access tothe object in response to receiving the intent associated with theobject; receive an indication that execution of one or more steps of theintent associated with the object is complete; and enter one or moreentries into an execution log, individual ones of the one or moreentries indicating completion of one of the one or more steps of theintent and ensuring execution of each of the one or more steps of theintent exactly once.
 20. The storage system of claim 19, the multipleinstructions further causing the processor to lock the object andprevent a computing device that is not requesting the object in order toperform the one or more steps of the intent associated with the objectin response to receiving the intent associated with the object.